Read AMA Morning Rounds®’ most popular stories in medicine and public health from the week of Dec. 29, 2025–Jan. 2, 2026.
Research uncovers evidence of four distinct types of autism
The Washington Post (12/26, A1, Cha) reported recent advancements in brain imaging, genetics, and computational science are uncovering evidence “for four distinct autism phenotypes, each defined by its own constellation of behaviors and genetic traits,” according to findings published in Nature Genetics. The analysis “suggests that some children may have genetic mutations when they’re born that activate at different times in life—a reflection of varying paths that emerge at different moments.” Such mutations “come from random copying errors in DNA or from outside influences. The list of suspects impacting autism is long: air pollution, paternal age, maternal diabetes, prenatal infections – all supported by some evidence, though none yet definitive.” Scientists are also exploring “external forces, particularly the prenatal environment, to find out what might nudge those genes to switch on or off.”
More than three in four U.S. adults may meet criteria for obesity under new definition
ABC News (12/29, Kekatos, Richards) reports a study found that “a new definition of obesity could nearly double the prevalence of U.S. adults with the condition.” Earlier this year, “The Lancet Diabetes & Endocrinology Commission...proposed a revised obesity definition that included waist circumference, waist-to-hip ratio and waist-to-height ratio. More than 70 medical organizations around the world have endorsed the definition but its use in practice has not been evaluated, according to the study authors.” Utilizing a new definition that includes waist-based measurements, the investigators “found that more than 75% of adults may meet criteria for obesity compared to 40% when using BMI alone.” Furthermore, “nearly four in 10 adults with a ‘normal’ BMI were found to have excess body fat when waist-based measures were also applied.” The study was discussed in a JAMA Network Open research letter.
Financial strain ages heart as much as classic risk factors for heart disease
HealthDay (12/29, Thompson) reports, “Fretting over making ends meet ages” the “heart just as much as classic risk factors for heart disease, a new...study says.” Investigators found that “financial strain and food insecurity are the strongest drivers of accelerated heart aging.” The data indicated that “the heart aging associated with money and food worries is similar to that caused by conventional risk factors like diabetes, high blood pressure and prior heart attack.” The research was published in Mayo Clinic Proceedings.
U.S. logs highest measles case total in decades
USA Today (12/31, Moniuszko) reported the U.S. “recorded 2,012 measles cases as of Dec. 23 [last] year, the highest total in more than 30 years, according to the Centers for Disease Control and Prevention.” CDC data indicate that the last time the country saw in excess of “2,000 cases was in 1992, or 33 years ago.” Propelling the totals for the year were “50 outbreaks, defined by the CDC as three or more related cases, reported across the country.” USA Today added that measles “was eliminated in the U.S. by 2000 but has resurfaced with periodic outbreaks, mostly among people who are not vaccinated.” During 2025, a total of 93% of measles cases were among individuals “who were unvaccinated or had an unknown vaccination status, CDC data shows.”
New flu strain driving surge across U.S.
The Washington Post (1/1, A1, Ovalle) reports flu cases in the U.S. are “rising, driven by a new strain that public health officials worry current vaccines may not protect against as effectively.” According to the CDC, “the number of hospitalizations, emergency room and outpatient visits, and deaths associated with the flu have shot up,” although the U.S. is not likely “to reach peak until early in the year, possibly February.” Overall, the CDC “estimates there have been at least 4.6 million flu-related illnesses, at least 49,000 hospitalizations and 1,900 deaths this season, which started in late September and may run through March or April.” The new strain “is a version of what is known as H3N2, a type of influenza A, and it’s quickly become the most common one in the U.S., according to the CDC.”
Reuters (12/31, Mahatole, Roy) reported that “among 275 viruses collected since September 28, 2025, which underwent additional genetic characterization at the CDC, 89.5% belonged to subclade K, a variant of the influenza A (H3N2) virus.” While severity indicators “remain low, flu activity is expected to continue for several weeks, the CDC report said. The agency urged anyone six months and older who has not yet received a flu shot to get vaccinated.”
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